When Will These Civil Aircraft Concepts Fly?

Airbus/Rolls-Royce E-Thrust

Developed with Rolls-Royce, E-Thrust is an Airbus concept for a future airliner with hybrid-electric distributed propulsion for reduced fuel consumption and emissions. The aircraft has a gas-turbine engine, energy storage system and electric ducted fans integrated into the airframe.

For takeoff and in the climb, the engine and energy storage system together provide peak power to the ducted fans. In cruise, the gas turbine powers the fans and recharges the batteries. On descent, the engine is switched off and the fans act as windmills to recharge the storage system. For landing, the gas turbine is restarted to ensure additional power is available for safety

Airbus Vahana Concept

In a departure for Airbus, its Silicon Valley outpost A³ plans to fly a full-scale prototype of an autonomous air taxi at the end of 2017. Project Vahana is developing an electric-powered, vertical-takeoff-and-landing aircraft with multiple propellers mounted on fore and aft tilting wings.

Vahana is designed to fly autonomously, carrying cargo or a single passenger over congested urban roads. If the prototype is successful, A3 plans to fly a production-representative demonstrator by 2020. Airbus is also working with Siemens to ready technology for a hybrid-electric airliner with under 100 seats by that time.

ESAero ECO-150

Entrepreneurial design company Empirical Systems Aerospace (ESAero) has developed the ECO-150 concept for an airliner with turboelectric distributed propulsion. The 150-seat ECO-150 has two turboshaft engines mounted mid-span on the wing, driving generators that power an array of 16 ducted fans embedded in the inboard split-wing sections.

Fuel savings of 20-30% over the Boeing 737-700 are projected for the conventional-electric ECO-150R version. The savings come from the effective increase in bypass ratio and propulsive efficiency with each turbine driving multiple fans. The split wing with its embedded propulsion also provides powered lift, due to the fans blowing at the trailing edge, requiring only simple high-lift flaps.

NASA STARC-ABL

NASA’s STARC-ABL—an acronym that stands for ‘single-aisle turbo-electric aircraft with an aft boundary layer propulsor”—is a relatively near-term concept for a 737-size airliner that can combine the advantages of hybrid-electric propulsion with today’s proven tube-and-wing configuration.

The design has an aft-mounted, electric-driven fan that provides propulsion while ingesting the boundary layer over the fuselage and reenergizing its wake to reduce drag. Generators on the main underwing engines produce the electric power, but the drag reduction allows use of smaller turbofans, saving fuel.

Boeing BWB

Conceived pre-merger by McDonnell Douglas and developed by Boeing, the blended wing body (BWB) concept is based on a wide fuselage mated seamlessly with high-aspect-ratio wings. The configuration is more aerodynamically efficient than conventional tube-and-wing transports because the entire aircraft contributes to the lift and, because it has less surface area than a comparable aircraft, produces less drag.

The BWB also offers structural gains due to the close integration of the centerbody with the wing. Maximum wing loads are significantly lower than for conventional configurations, providing weight savings. In addition, the engines are located on the aft upper surface, providing natural noise shielding that makes the configuration quieter during takeoff and landing.

Lockheed Martin HWB

Conceived by Lockheed Martin, the Hybrid Wing Body (HWB) combines a blended forward/center fuselage and high-aspect-ratio-wing for aerodynamic and structural efficiency, with a conventional aft fuselage and T-tail for compatibility with existing airlift infrastructure and airdrop procedures.

Developed with the U.S. Air Force Research Laboratory, and further refined with NASA, the HWB also features an unusual propulsion arrangement that houses the engines in overwing nacelles. Cantilevered on struts over the trailing edge, the overwing positioning enables higher-bypass-ratio engines and is predicted to have 5% less drag than conventional underwing engines. The configuration also provides acoustic shielding and, at low speed, increases aircraft lift without a thrust or drag penalty.

Bauhaus-Luftfahrt

German design house Bauhaus-Luftfahrt, in which Airbus is a shareholder, has developed the Propulsive Fuselage concept for an ultra-efficient airliner. The configuration mounts a fan in the tail, where it ingests air flowing over the fuselage via an annular inlet and re-energizes the wake, reducing drag and fuel burn.

The initial concept has two conventional turbofans under the wings and a third gas turbine in the tail to drive the fuselage fan via a gearbox, but Bauhaus has also studied a turbo-electric configuration in which generators on the underwing turbofans drive the fuselage fan electrically.

Aurora/MIT D8

Conceived for NASA by the Massachusetts Institute of Technology, the “double-bubble” D8 is being further developed by Aurora Flight Sciences. The 180-seat aircraft has a wide lifting fuselage with a non-circular cross-section that allows a twin-aisle cabin in a market now served by the narrowbody A320 and 737.

The major innovation in the D8 is boundary-layer ingestion. Turbine engines embedded in the tail drive distortion-tolerant fans that ingest the slow-moving air over the upper fuselage and reenergize the wake, reducing drag. Aurora is targeting a fuel-burn reduction of 49% over the 737-800.

Boeing TBW

Developed by Boeing under the NASA-funded Subsonic Ultra Green Aircraft Research program, the transonic Truss-Braced Wing (TBW) concept derives its high aerodynamic efficiency from a slender, glider-like wing with an aspect ratio of more that 19.5 compared to 11 for the composite-winged Boeing 787.

Compared to a conventional cantilevered wing, a braced wing can theoretically be lighter because the strut relieves some bending moment. This enables a larger wing for the same weight. The longer the wing, the higher the potential lift-to-drag ratio and lower the induced drag. Struts also allow a thinner wing, significantly reducing wave drag at transonic speeds. The thinner profile is more suitable for natural laminar flow, as well, further reducing drag and enhancing efficiency.

Dzyne Ascent

Traditionally, studies show the aerodynamically and structurally efficient blended wing body (BWB) configuration works well for large transport aircraft but less so for smaller regional and business jets. This is because the double-deck design, with passengers above and cargo and landing gear below, results in a deep centerbody and a blended wing that is too thick for efficient transonic flight.

But design house Dzyne Technologies has a concept that moves the gear outward and stores baggage and cargo in the wing roots, outboard of the cabin, reducing the thickness of the centerbody and blended wing. Dzyne has a concept for a 110-130-seat “super-regional” burning 20% less fuel than existing narrowbody designs. As a business jet, essentially the same aircraft has three times the floor area of long-range, large-cabin aircraft such as the Gulfstream G650, the company says.

Onera NOVA

Under the Next-generation Onera Versitalie Aircraft (NOVA) project, the French research agency is studying two concepts for a future 180-seat airliner to succeed the A320. Both assume future aircraft will have to accommodate turbofans with much higher bypass ratios and fan diameters than today’s engines.

One design has geared turbofans still mounted under the wing, but with increased dihedral inboard creating a “gull wing” to accommodate bigger nacelles without lengthening the gear. The other design has the engines embedded in the tail, where they ingest the low-energy boundary layer flow over the fuselage and reenergize the wake to reduce drag.

Rolls-Royce DORA

Developed by Rolls-Royce with the UK’s Cranfield University, the Distributed Open Rotor (DORA) concept combines two key fuel-saving technologies: turbo-electric distributed propulsion and open-rotor powerplants. The design also has a slender high-aspect-ratio wing and V-tail to minimize drag.

Two turbogenerators mounted outboard on the wing drive eight electric motors and propellers installed along the inboard leading edge. This increases the effective bypass ratio of the propulsion system and capitalizes on the high propulsive efficiency of open rotors to reduce fuel consumption and emissions.

Agreed. When I read through the descriptions, I see improvements of efficiency of 20% or so over the 737-700. We already have two products that reac that level of improvement; they're called the 737 MAX and 32x NEO.

I hope to see BWB/HWB aircraft sometime in the future (probably 20 years out) as they do offer significant efficiency and volume carrying improvements over current designs but I don't see anybody ponying up the cash for them now, which would mean they're flying in 10 years.

None. For many of these concepts, it can't be efficient to spend fuel to lift heavy batteries. And at some point, the mass hysteria on "emissions" is going to fizzle, when "denying" man-made climate change becomes mainstream.

Lifting batteries is just another trade-off. Present batteries are rather low energy density for aviation use, but that doesn't mean that batteries 10 years out won't be. Also, electric motors are so efficient (> 90%) compared to their combustion counterparts that there is a strong incentive to use them wherever possible. And BTW denying climate change is equivalent to denying physics. Change the state of a system by applying a forcing, such as CO2 levels, and it will move to a new equilibrium state, which if you have to live in it may be one you don't like. And denying that burning fossil fuels releases CO2 is denying chemistry. Be my guest, but don't expect me to take you seriously.

"Vahana is designed to fly autonomously, carrying... .a single passenger over congested urban roads."
The bleeding-heart tree-huggers will never allow this. We must car pool and enjoy togetherness.
The Onera NOVA is the closest to a pusher propeller, so I vote for it.

Why expend so much energy with VTOL single passenger vehicles?
The wheel is an amazingly efficient invention.
Unless all the energy comes from abundant sustainable sources, but then you NON-tree-huggers don't like that idea.

Neither is driving one's "1 ton" pickup five miles to and from work every day. Many people do that though. Add the stop and go traffic and stoplights and the effective milage of an electric VTOL scooter may not compare too poorly.

The efficiency of thin wings is an attractive proposition, but they offer little space for batteries and/or fuel. We all know the rules about fuel in civil fuselages, but will customers be happy sitting above Lithium Polymer cells?

From the choices given and the economic climate, I predict that only the cheapest to develop, with lowest risk and use of existing proven technology will be most likely to appear in the next decade.
(Come on Musk, Bezos, Branson, prove me wrong!)

How about a bizjet scaled demonstrator of the Luftfahrt concept?
Get rid of that horrible tail complexity by using a Beech Starship config. with tip fins.

As for aalexandre's picks:
- At a number of angles, the P-51 is downright ugly. It has a very deep and somewhat short fuselage - not like the (early mark) Spitfire that is elegant, no matter how you look at it.
- The F-14 is too lumpy to ever be called attractive. It's very functional, purposeful as well as powerful but I wouldn't call it attractive.
- I would agree that the Rafale is a good looking aircraft, good proportions with functional pieces (ie the canards) bringing the lines of the aircraft together.

Also, you're comparing military aircraft to civilian ones. I've never found the tube and wing approach to be particularly attractive, so the concepts presented here, providing a new perspective on civilian transports that seem to catch my eye more than say a B-787 or A350 will ever do.

"Personally, I think most of these concepts are very attractive. " I agree in the sense of technological achievements, but for me a bird must sing!!!
An A350 or B787 are boring they are not making any sound at all!!! I prefer a good old fashioned 707 or 747. So do the Concorde!
At Sigonella airbase a bunch of super-hornets landed and at 100km/h as a passenger unfastened my belt, took it and sat on the window car opened and took some pictures. Those are pretty birds. So are MIGs and SUs!
Passengers birds are nothing more than fat buses.
I am not questioning the millstones made with those concept nor the solutions!

"I predict that only the cheapest to develop, with lowest risk and use of existing proven technology will be most likely to appear in the next decade."

Sound based upon 114 years of aerospace history.

"So, we must incorporate 'Beauty' into efficient planes of the future to make you happy?"

Airplanes don't need to be beautiful to be somewhat successful. Take the Farman F.120 Jabiru for example. More of a commercial success was the Handley Page Heyford. I personally have always had a soft spot in my heart for the quite successful Breguet Deux-Ponts. And who can't love the PL-11 Airtruck!

Another alternative would be the HSB, High Staggered Biplane configuration, proposed in may 2007-01-2957 SAE paper on Fuel cell driven airplanes which by the way is similar to the Airbus Vahana air taxi configuration also used in the higlhy eficiente Burt Rutan´s Quickie home buit small airplane.

I do not think the question should be when will “these civil aircraft concepts fly” but rather, the technology concept. It appears evident that several new design concepts have an aft mounted fan to “re-energize” the wake for drag reduction and efficiency gain. I would imagine this technology could be fairly easily incorporated into existing airframes similar to the addition of winglets on older aircraft.

It's Interesting that Boeing's TWB concept of a wing struts jet airliner was contemplated by the small French company Hurel Dubois in the late 50's as a competing design with the Sud Aviation Caravelle. The rest is history. Wonder where commercial aviation would have gone had the design been carried out.

does anyone really think robot controlled VTOL aircraft with un-ducted props will be a practical, real world option? Safety and noise will kill that plan, imagine dozens of them buzzing around in confined places like urban areas, there seems to be an attitude by some of the developers that they can be as simple to maintain and cheap as cars-not so! This is a good place for NASA to be doing research ( high efficiency aircraft), better use of tax money than sending people into space.

Some cities are trying to establish/restore a tree canopy. Already I can't see what stores are in the shopping centers due to the trees planted in the parking lot islands. Miami has gone insane with tree planting on every road edge and median divider. No flying is possible here without reconfiguring the landscaping.

Perhaps Graham didn't have nice concept art to post, but let's not forget the secretive projects Larry Page is (allegedly) bankrolling at Joby, Kitty Hawk, and Zee. There's even more potential vaporware to gawk at with Boom, Elytron, and XTI. Rumors are that Zee has had air under the wheels, so maybe it can't be part of this list. Equally, the Tier 1 kit-bash electrification of a Robinson helicopter probably is disqualified from the competition for next to fly.

I guess it's unfair to avoid answering the question. Of these concepts, probably the DORA concept will fly first, with NASA demonstrating the X-57. The other concepts will have to wait their turn to have their Achilles heels exposed in flight test. Thankfully, AFRC has access to a long long long runway on which to land Maxwell. I hope the others choose safe, appropriate flight test facilities.

For over 100 years of aviation history that "Truss Braced Wing" was known as a Strut braced wing.

Strut sounds so old fashioned that now we have to dissemble and call that diagonal member transferring lifting loads from the outer wing to the lower fuselage a "Truss."

Let us put the Public Relations Bravo Sierra aside and examine the component words of the newspeak term "Truss Braced Wing."

The word Wing is not being misused. The word “truss” is.

definition of strut
1 : a structural piece designed to resist pressure in the direction of its length

Definition of truss
1 : an iron band around a lower mast with an attachment by which a yard is secured to the mast
2 a : bracket
2 b : an assemblage of members (such as beams) forming a rigid framework

The Boeing design uses a Strut to connect the Wing and Fuselage to form a Truss.

Anyone wishing to see a "truss braced wing” check out the Handley Page HP.42. Note that the truss bracing the wing is composed of struts.

wikipedia.org/wiki/Handley_Page_H.P.42

The Boeing "Truss Braced Wing" must have been named by someone in the public relations racket, not an honest engineer or lexicographer.

We can't have a jet airliner with struts, can we? It sounds so Cessna 150. . .

Quick Winston Smith at the Ministry of Truth. Search 100 years of Aviation Week and cast all mention of Struts down the Memory Hole and replace them with Truss; or you will visit the Ministry of Love.

“You are a slow learner, Winston."
"How can I help it? How can I help but see what is in front of my eyes? Two and two are four."
"Sometimes, Winston. Sometimes they are five. Sometimes they are three. Sometimes they are all of them at once. You must try harder. It is not easy to become sane.”
― George Orwell, 1984

We have been over this before here. As you correctly say,a strut is a single structural piece and a truss is an assemblage of members. The concepts NASA has studied range up to 777 size and have bracing schemes ranging from single struts up to multiple members, so the term "truss-braced" was adopted to cover the range of possibilities and to differentiate the concepts from light aircraft with wing struts

At what point does 2+2=5? Is there a specific gross weight at which an aircraft becomes "truss braced"? For example 12,500 pounds?

Or does any aircraft propelled by one of those Blower Doohickies* become "truss braced" when it has a maximum speed of over 110 knots and a stall speed over 60 knots, excluding, for example the PZL M-15 Belphegor?

*Blower Doohicky is the Bureau of Absurd Nomenclature designation for a reaction propulsion unit attached to any airplane that is not spiffy enough to be called a jet.

“But it was alright, everything was alright, the struggle was finished. He had won the victory over himself. He loved Big Brother.”
― George Orwell, 1984

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